1. Field of the Invention
The present invention relates to a figure-forming composition, a production process of three-dimensional figures or structures, and three-dimensional living body models. In particular, the present invention relates to a figure-forming composition having characteristics of attaining a prescribed hardness with a small amount of water by basically containing a relatively large amount of polyvinyl alcohol resin (and hardening accelerator). The present invention also relates to a method for obtaining three-dimensional structures having desired hardness by adding enough water (preferably water and cross-linker) to sophisticated three-dimensional figures which is rapidly formed by accumulating a plurality of layers patterned with a little moisture by using the figure-forming composition. The present invention further relates to a technique of producing custom-made three-dimensional living body models by using the method for producing three-dimensional structures.
2. Description of the Related Art
In the orthopedic medical field, for example, there is a demand for surgery training using three-dimensional living body models such as bone parts. There is also a demand for having a concrete image of a surgery beforehand to prepare for a real surgery by using a three-dimensional model of a part including a diseased site of a patient. However, it was difficult to obtain custom made three-dimensional living body models. In addition, three-dimensional living body models contain wax which leaks out when sterilization procedure was performed to the models. So, the models can not be used in operating rooms.
In recent years, rapid prototyping apparatus for easily forming three-dimensional structures (shown in, for example JP-T 2001-524897, JP-T 2003-531220, JP-T 2004-538191, JP-T 2005-503939, U.S. Pat. No. 5,204,055 specification, U.S. Pat. No. 5,340,656 specification, U.S. Pat. No. 5,387,380 specification, U.S. Pat. No. 6,007,318 specification, U.S. Pat. No. 6,375,874 specification, U.S. Pat. No. 5,902,441 specification and U.S. Pat. No. 6,416,850 specification. These are incorporated herein for reference purposes) and rapid prototype process are increasingly used. Three dimensional objects, such as prototype parts of apparatus, are used to examine the performance thereof. The prototype parts have been produced by injection molding. Compared with a conventional method such as injection molding, the rapid prototype process has greater advantage in terms of time and cost. The examples of rapid prototype method include stereolithography method, powder sintering method, powder binding method, and solid ground curing technology (SGC), which forms thin layers based on a cross sectional shape data to form three-dimension shape by laminating the thin layers.
Stereolithography is a method for forming three-dimensional shape by laminating thin layers by repeating the following processes: solidifying thin layers by irradiating laser beam to liquid light curing resin accommodated in a container based on cross-sectional shape data of three-dimensional objects to be formed, followed by pouring the same liquid light curing resin on the thin film and irradiating laser beam thereto. However, the light curing resin is difficult to handle because it is highly photoreactive and also it is in a liquid state. There is also a problem that the accuracy of formed objects is not always high because the resin shrinks when it is hardened.
The powder sintering method laminates thin layers which are formed from powders, instead of light curing resin used in stereolithography, by sintering powders with laser beam irradiation. With this method, three-dimensional structures can be formed with metals and ceramics. However, there are problems that high-power laser must be used to sinter powders and the optical control is difficult.
In the powder binding method, powder materials are used as well. But in contrast to the powder sintering method, thin layers are accumulated and solidified by using adhesive agent. With this method, three-dimensional structures can be formed relatively quickly. But, since this method uses adhesive agent to bind powder materials, the resultant structures do not have enough hardness. This method also has a problem that the layer structure is not continuous because layers are bound together with adhesive agent.
Solid ground curing technology (SGC) is as follows. Firstly, a mask pattern is formed based on cross-sectional shape data and ultraviolet irradiation is performed on this mask pattern which is accumulated on a resin layer on which light curing resin is applied. Having performed enough ultraviolet radiation, unhardened ultraviolet resin layer is removed, and heat-hardening resin is filled in the depressed area which is formed by removing the unhardened ultraviolet resin layer. Then, the filled heat-hardening resin is hardened, a thin layer composed of hardened ultraviolet hardening resin and hardened heat-hardening resin is formed. Having this thin layer laminated into a three-dimensional structure, ultraviolet hardening resin is dissolved. With this technology, there is a problem of noise when the unhardened ultraviolet resin layer is removed by suction. There is further a problem that highly qualified three-dimensional shape cannot be obtained.
Japanese Patent Laid-Open No. 10-207194 discloses a laminate molding method for molding three-dimensional objects by laminating thin layers which is formed from powder material in a sheet shape. It shows “a laminate molding method for forming three-dimensional objects comprising the steps of: forming electrostatic latent image on the surface of a dielectric, based on arbitrary cross-sectional shape data of a three-dimensional object; developing the electrostatic latent image with electrifiable powder; forming the electrifiable powder in a sheet shape; and copying the sheet-like electrifiable powder on a stage. By repeatedly performing the above steps, sheet-shaped electrifiable powder material is laminated and a three-dimensional object is molded.”
However, in the method for molding three-dimensional objects, disclosed in the Japanese Patent Laid-Open No. 10-207194, basically, thin layers of electrifiable powder material are formed and laminated to form three-dimensional structures by using electrophotographic photoreceptor drum. So, the method is not suitable for forming three-dimensional structures using materials like gypsum.
Japanese Patent Laid-Open No. 2002-67174 discloses a data processing apparatus for generating molding data to be used in three-dimensional molding, “which comprises: a shape data inputting means for inputting shape data regarding shape of an object; a feel information acquiring means for acquiring feel information regarding texture of the object; and a data generating means for generating the molding data for duplicating the shape and feel of the object on the basis of the shape data and the feel information.” This apparatus is considered to be able to duplicate the feel of objects precisely.
The Japanese Patent Laid-Open No. 2002-67174 discloses a rapid prototyping apparatus used for powder molding method and powder sintering method. But an apparatus using gypsum in particular is not disclosed.
Japanese Patent Laid-Open No. 2005-148578 discloses a technology for producing rigid three-dimensional model in which layers of gypsum powder are obtained based on layer data of objects, and the layers are laminated by being fixed with binders (see paragraph [0008] and [0026] of the bulletin).
However, the technology disclosed in the Japanese Patent Laid-Open No. 2005-148578 is mainly related to producing three-dimensional models of organs which characterizes to soften the rigid three-dimensional model obtained by laminating materials such as gypsum. (see, for example, claim 14 and paragraph [0022] to [0034]). So, the process of producing rigid three-dimensional models from gypsum powder is not described in detail. Also, since it is aimed at producing three-dimensional model of organs, which does not have hardness like that of bones, the resultant three-dimensional models are not always suitable for surgical training. Furthermore, the resultant three-dimensional models are not intended to go through autoclave treatment, and so the models are generally soaked in wax, or the binders contained includes wax ingredient. As a result, when the three-dimensional model is heated in an autoclave, wax ingredient elutes therefrom, and the form and the hardness thereof changes.
On the other hand, gypsum is widely used for building material and three-dimensional models. For example, Japanese Patent Laid-Open No. 63-25021 discloses a technology for mixing polyvinyl alcohol fiber in hemihydrate gypsum (see line 9 to 16 upper left). But, the polyvinyl alcohol fiber is cited only as an example of ingredient mixed in gypsum to prevent a gypsum mold from cracking.
In the field of building material, it is known that polyvinyl alcohol resin is mixed with hemihydrate gypsum in order to raise the hardness of gypsum compact. For example, JP-A 05-319890, JP-A 08-337459, JP-A 09-48681, and JP-A 2000-178064 discloses inventions using gypsum and polyvinyl alcohol resin.
The JP-A 05-319890 discloses “a gypsum composition prepared by mixing powders of polyvinyl alcohol based polymer, 90% of which is dissolved in water at 80 degrees Celsius for 20 minutes (A) and powders which can thicken the polyvinyl alcohol based polymer (B) with powders mainly containing hemihydrate gypsum (C)”. In the embodiment of JP-A 05-319890, 100 weight parts of hemihydrate gypsum is mixed with 1 part by weight of carboxyl group modified polyvinyl alcohol, with polymerization degree of 1750, saponification degree of 98 mol %, particle size of 30 mesh path, which is 2 mol % maleic acid copolymerized. However, since the content of polyvinyl alcohol resin is small, enough hardness can not always be obtained with a little amount of water. But in JP-A 05-319890, since the gypsum composition is intended to be used in the form of slurry, there is no problem even if the content of polyvinyl alcohol resin is small.
The JP-A 08-337459 discloses “gypsum composition which can be hardened and forms a water-resistant gypsum product by hydration, comprising a mixture of: a) 100 weight parts of gypsum, and b) 0.5 to 20 weight parts of aqueous emulsion solids, per 100 weight parts of gypsum, wherein the aqueous emulsion comprising water and: i) a paraffin hydrocarbon having a melting point of 40 to 80° C.; ii) montan wax in an amount of about 1 to 200 weight parts, per 100 weight parts of the paraffin hydrocarbon, and iii) polyvinyl alcohol in an amount of about 1 to 50 weight parts, per 100 weight parts of the paraffin hydrocarbon.” (see claim 4 of the bulletin) However, since the gypsum composition contains paraffin wax, when the molding is placed in an autoclave, wax ingredient elutes therefrom, and the form and the hardness thereof changes.
The JP-A 09-48681 discloses “gypsum hardened body whose surface is coated with acrylic emulsion, vinyl acetate emulsion or polyvinyl alcohol coating material”. In the bulletin, polyvinyl alcohol coating material is disclosed as material applied on the surface of gypsum hardened body.
The above JP-A 2000-178064 discloses “gypsum hardened body comprising gypsum, polyvinyl alcohol resin, and fluorinated compound” (see claim 1 of the bulletin). It is preferred that “1 to 30 weight parts of polyvinyl alcohol resin (further preferred 5 to 20 weight parts) is included, per 100 weight parts of gypsum” (see paragraph [0009] of the bulletin). However, the gypsum hardened body disclosed in the bulletin contains fluorinated compound as an essential element, and as disclosed in paragraph [0011], it is intended to be mixed with water.
JP-T 2003-531220 discloses a composition for three-dimensional printing of solid objects. However, it does not particularly use calcium-based material nor polyvinyl alcohol derivatives. So, it was difficult to obtain sophisticated three-dimensional figures by RP process in a short period.
JP-T 2001-524897 discloses a method for producing molded bodies which is formed from powder material by repeating the steps of: forming a layer of powder material, applying powder material in water pattern, and forming a layer of powder material combined in pattern (see claim 1 of the patent). And in the embodiment, polyvinyl alcohol itself was used as powder material, and a molded body was obtained. (see page 9 of the bulletin). However, when only polyvinyl alcohol is used, it is difficult to obtain molded bodies by PR process.
The object of the present invention is to provide a figure-forming composition which initiates hardening even with a small amount of water, and can attain a prescribed hardness, and which is suitable particularly for producing three-dimensional living body models for surgery training by a rapid prototype process.
The object of the present invention is to obtain three-dimensional figures which are for example tentative structures to obtain three-dimensional structure living body models such as three-dimensional living body models, implants or artificial bones by using the above figure-forming composition.
The object of the present invention is to obtain three-dimensional structures such as three-dimensional living body models, implants or artificial bones. In particular, it is an object of the present invention to obtain three-dimensional structures, which is relatively uniform and sophisticated, and are not be deformed in high temperatures in an autoclave and the like.
The object of the present invention is to provide custom made three-dimensional living body models which can be used for surgical training, explanations of surgical planning, and explanations of bone or tooth site of patients' in front of the patients, and implants and artificial bones having desired shapes to be embedded.